1. Field of the Invention
The present invention generally relates to an inflatable structure, and more particularly, to an inflatable robotic arm for use in low gravity and weightless environments which provides a low volume, low weight transportation alternative to conventional rigid robot arms.
2. Background
The use of robotic systems in outer space provides an extension of man's capabilities while decreasing the potential risks and hazards encountered in the hostile environment of space. One particular example of such robotic systems is the manipulator arm used by NASA on the Space Shuttle.
A constraint on the use of robotic systems in outer space is the high cost of transportation to the intended site of use resulting from the relatively large and heavy conventional manipulator arms and motors currently employed. Additionally, the overall size of the conventional manipulator is further prohibited thereby constraining the availability of such devices for use in outer space.
Robotic devices have been disclosed which have members which are inflatable to form rigid or semi-rigid structures, such as described in U.S. Pat. Nos. Re. 28,663, 3,347,587, 3,574,386, 3,601,442, 3,713,685, 3,716,264, 3,913,307, 3,945,486, 3,981,528,4,751,868, 4,784,042, and 4,815,782. However, none of these robotic devices make any provision for controlling movement of the inflated rigid structure using a motor positioned at a base so as to provide a lightweight inflatable robot arm having a low moment of inertia.
Therefore, one object of the present invention is to provide an inflatable rigid structure for use as a robotic arm which has a low moment of inertia so that the length of the robotic arm can be increased as desired without compromising the structural rigidity of the inflated rigid structure.
Another object of the present invention is to provide an inflatable structure having low inertia employing a driving arrangement which permits the use of small lightweight motors to reduce the overall weight of the structure.
Still a further object of the present invention is to provide an inflatable rigid structure for use as a robotic arm having a driving arrangement for manipulating the inflated structure which is positioned so as to further reduce the moment of inertia of the robotic arm of the inflatable rigid structure.
A further object of the present invention is to provide an inflatable structure for use as a robotic system in outer space which dramatically reduces transportation costs involved in delivering the structure to the intended site of use.
Yet a further object of the present invention is to provide an inflatable structure for use in outer space which is relatively lightweight and compact during transportation in a deflated state and provides the capabilities of a conventional manipulator arm when inflated.
Still another object of the present invention is to provide an inflatable structure providing a substantial payload/machinery weight ratio to provide profound cost savings for space-based applications.
These and other objects, advantages and features of the present invention are achieved, according to one embodiment of the present invention, by an inflatable structure comprising an elongated link formed of a flexible fluidtight material and defining at least one fluidtight chamber. The material of the link has sufficient strength to remain fluidtight when the at least one chamber is inflated with a fluid to a pressure sufficient to rigidize the link. The inflated elongated link is pivotally connected at a base at which a drive arrangement is provided such that a position of the link can be controlled when the link is inflated. Additionally, a controllable manipulator or the like can be positioned at an outer end of the inflated elongated link.
According to a further embodiment of the present invention, an inflatable articulated structure is provided having at least two elongated links, each of the links being formed of a flexible fluidtight material and each defining at least one fluidtight chamber. The two elongated links are pivotally connected by a pivot joint arrangement and a drive arrangement is provided such that a position of the links can be controlled with respect to one another when both links are inflated. As with the single link arrangement, the articulated structure of this embodiment has the drive arrangement for controlling the position of the articulated links provided at the base of the structure to thereby reduce the overall moment of inertia of the articulated links and permit the use of small, lightweight motors.
One particular advantage provided by the inflatable structure of the present invention is the ability to deflate the elongated link of the structure thereby reducing the overall size and volume of the structure during transport into outer space.
Additionally, the utilization of a low inertia and lightweight inflatable link permits the use of smaller motors than used by conventional heavy, rigid manipulator arms, thereby further reducing both the weight and cost of the structure while providing the same advantages of conventional manipulator arms. Moreover, by positioning the various drive motors employed to drive the link at the base of the structure, the moment of inertia of the link is further reduced thereby decreasing the amount of force needed to start and stop the link as required.
A further advantage of the present invention is provided by the substantial increase in the payload/machinery weight ratio which is on the order of ten-fold or more as compared to conventional rigid robot arrangements currently available.
One particular feature of preferred embodiments of the present invention is that the link can be inflated with a fluid, for example, with air, to pressures sufficient to provide the required stiffness, for example, between 10 psi to 50 psi or more, in order to provide the requisite stiffness of the link. Additionally, fluids other than air can be employed to inflate the link, including, such as, for example, liquids, helium or gases produced by gas generators of any kind.
The fluidtight chamber of the link can be further divided into a plurality of individual cells such that when one cell is deflated or damaged, the rigidity of the link is still maintained. Further, self-repairing or self-sealing materials can be employed to form the link to prevent or reduce leakage of fluid from a damaged link.